Rotary cutting dies are used to cut and score sheets of corrugated board to produce die cut products that can be manipulated into boxes. Rotary cutting dies typically include a curved die board that is configured to mount on a die cylinder. When used, the die cylinder and die board are mounted adjacent an anvil and a nip is defined between the cylinder and the anvil. Sheets of corrugated board are fed into and through the nip and, in the process, the sheet of corrugated board is cut and scored to form the die cut product. Die boards commonly include product and scrap cutting blades, scoring rules, trim and scrap strippers and product ejectors for separating the die cut product from the cutting die.
A common problem with rotary cutting dies that operate on corrugated board is that of controlling the pressure exerted against the corrugated board by the product ejectors. If the pressure is too great, the die cut product is damaged. That is, if the pressure is too great, the corrugated flutes are crushed. This makes the resulting boxes weaker and hence the boxes possess less stacking strength and the crushed flutes have a negative impact on the appearance of the product. The appearance of the product is especially important if the corrugated board is printed.
On the other hand, if the ejection force exerted by the product ejectors is too low, then this will impact the separation of the die cut product from the cutting die during the die cutting operation. That is, if the force is insufficient to dislodge or remove the cut die product from the cutting die, it follows that the product will continue with the cutting die and the die cutting operation will be seriously impacted.
The problem is applying sufficient pressure to the die cut product to separate it from the cutting die but at the same time limiting the pressure to a pressure that will not crush the flutes of the die cut product. There are tried and proven materials for product ejectors that have been used in the past. Generally in the past, pressure constraints were not as important as they are today as the corrugated board could withstand relatively high pressures without the flutes crushing. However, there is a trend in the industry of employing corrugated board having flutes that are more easily crushed. Therefore, there is now a need for a product ejector that will efficiently separate die cut product but lend themselves to controlling and limiting pressures that will not crush flutes in the die cut product.